A light emitting diode (LED) lamp using a direct-current (DC) LED device as the filament must be equipped with a power converter for converting the alternating-current (AC) power voltage into a DC input voltage for the DC LED device. The power converter not only requires additional component cost for the LED lamp, but also cannot fit entirely into the standard lamp bases of ordinary light bulbs. For a LED lamp to be equipped with a power converter, it is necessary to develop special molds to produce containers and corresponding mechanism different from those of ordinary light bulbs to fit the power converter therewithin, which nevertheless increases the cost and volume of the LED lamp. On the other hand, a DC LED device generates heat when it is powered on and therefore, an additional heat dissipation mechanism is required to handle the heat. If the heat is not effectively dissipated, the resulting high temperature will reduce the emissive efficiency and service life of the DC LED device and produce other adverse effects such as wavelength shift. Moreover, the power converter, particularly the inductor and integrated circuit therein, also generates heat during power conversion, and the consequent high temperature may damage the inductor and integrated circuit and cause failure of the LED lamp accordingly. The problems caused by insufficient heat dissipation are aggravated especially in high power applications, such as in lighting fixtures for illumination purposes, where the DC LED device generates relatively more heat. To adapt to the relatively small space within ordinary lamp bases, some LED lamps use a plurality of low power lamp type LED devices in conjunction with a simple bridge rectifier circuit. However, low power LED devices are poorly accepted in the market due to their generally low brightness, and these LED lamps tend to have serious light attenuation problems as a result of poor heat dissipation.
In recent years, AC LED devices are maturing technically, have improved in brightness, and therefore have had commercial value. An AC LED device includes a plurality of serially and/or parallel connected LED electronic elements manufactured on an epitaxial chip. The epitaxial chip is packaged and then connected in series with a resistor having a particular resistance so as to withstand high voltage, e.g., 110 V or 220 V, mains electricity, thus dispensing with the power converter or rectifier circuit required for a DC LED device. In consequence, the cost of an AC LED lamp is lowered in comparison with its DC counterpart, and the circuit related quality issues reduced. An AC LED device, though conveniently applicable in small spaces, still demands heat dissipation. This is especially true in high power applications, such as lighting fixtures for illumination purposes, where the AC LED device generates relatively more heat. If a heat dissipating device is added, the resultant LED lamp will be bulky and costly. However, if no additional assistance is provided to enhance heat dissipation from the AC LED device, the emissive efficiency and service life of the AC LED device will be reduced, wavelength shift is likely to happen, and even worse, the LED epitaxial chip may be burned out.